1. Earthquakes What Is An Earthquake? Click here to find out
Liz LaRosa
for my 5th grade science class 2009
What Is An Earthquake? Click here to find out

2. What is an earthquake?
Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
Caused by volcanic or plate activity,
The map above shows the distribution of earthquakes with magnitudes greater than 5.0 that occurred between 1965 and 1995.

3. Three Types of Faults Strike-Slip Normal Reverse
Animation of fault movement
Strike-Slip
Reverse
Three types of faults
Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks
Strike-slip
Normal
Thrust
Normal

4. Normal fault
Pulls on the crust stretching rock so that it becomes thinner (like pulling on bubble gum) = tension
Occurs when plates are moving apart
Hanging wall
Foot wall
Results in hanging wall slipping downward
animation

5. What type of fault? normal Hanging wall Foot wall
Normal fault - Results in hanging wall slipping downward

6. What causes earthquakes?
Tectonic plates move past each other causing stress. Stress causes the rock to deform
What type of fault boundary is this?
What type of stress is shown?
transform
shearing
Transform plate boundary showing shearing stress.

7. Strike – slip fault
Rocks on either side of fault slip past each other sideways with little up or down motion -
What type of stress is produced?
shearing
Occurs at a plate boundary
transform
Animation of strike-slip motion

8. Fault rupture across road in western Kaynasli, right-lateral strike slip displacement was about 4.0 m (13 feet) at this location

9. Reverse fault
Pushes on the crust squeezing rock until it folds or breaks (like a trash compactor) =
Occurs when plates are moving together
compression
Hanging wall
Foot wall
Results in hanging wall slipping upward
animation

10. What type of fault? reverse Hanging wall Foot wall
Reverse fault – hanging wall has moved upward

11. What type of fault?

12. Focus
– 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly
Epicenter 2 1

13. How Seismographs Work
A seismograph is an instrument used for recording the intensity and duration of an earthquake.
the pendulum remains fixed as the ground moves beneath it
Contrary to intuition, an earthquake does not make the pendulum swing. Instead, the pendulum remains fixed as the ground moves beneath it.
A pendulum with a short period (left) moves along with the support and registers no motion. A pendulum with a long period (right) tends to remain in place while the support moves.
The boundary between the two types of behavior is the natural period of the pendulum. Only motions faster than the natural period will be detected; any motion slower will not. 

14. Earthquakes How are earthquakes measured?
Seismogram – seismic wave display record
Seismograph machine

15. Seismic Waves

16. Primary Waves (P Waves)
A type of seismic wave that compresses and expands the ground
The first wave to arrive at an earthquake

17. Secondary Waves (S Waves)
A type of seismic wave that moves the ground up and down or side to side

18. Comparing Seismic Waves

19. Surface Waves Move along the Earth’s surface
Produces motion in the upper crust
Motion can be up and down
Motion can be around
Motion can be back and forth
Travel more slowly than S and P waves
More destructive
Animation of wave types

20. How do scientists calculate how far a location is from the epicenter of an earthquake?
Scientists calculate the difference between arrival times of the P waves and S waves
The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

21. Typical Seismogram How much time elapsed between the arrival of the
P wave (start) and the arrival of the S wave (finish)?
finish
start
Approximately 5 minutes and 20 seconds.

22. Locating Earthquakes

23. Locating Earthquakes

24. Now you are going to be seismologists and locate an Earthquake
Go to:
Click here to go to virtual earthquake site

25. National Geographic earthquake information

26. How are Earthquakes Measured? Richter Scale
A logarithmic scale used to express the total amount of energy released ___________ of an earthquake. Its values typically fall between 0 and 9, with each increase of 1 representing a _________ increase in energy.
magnitude
10-fold

27. How are Earthquakes Measured? Mercalli Intensity Scale
A scale of earthquake intensity based on ___________
and ranging from I (detectable only with instruments) to XII (causing almost total destruction).
observed effects
Click for Interactive Demo
Go to

28. Earthquake Waves & Earth’s Interior
Seismic wave animation

29. Seismic Waves in the Earth
Click here for animation

30. Click here for explanation of a tsunami
Tsunamis
Click here for explanation of a tsunami

31. Formation of a tsunami
a large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
PBS –tsunami animation

32. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!
Click here for Japan helicopter view of tsunami

33. Tsunami Warning System

34. Review Questions
1. A large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
tsunami
2. Used to describe both a sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
earthquake

35. How are Earthquakes Measured?
3. Which one uses a logarithmic scale to express the total amount of energy released or magnitude of an earthquake.
Richter Scale
4. Which uses a scale of earthquake intensity based on observed effects and ranging from I (detectable only with instruments) to XII (causing almost total destruction).
Modified Mercalli Scale

36. What type of fault is shown by each picture?1. 2.
Normal
Reverse
Transverse or strike-slip 3.

37. Which type of wave travels through solids only?
S-wave

38. Which type of wave causes the most destruction?
Surface or
Love waves

39. What type of fault? B A Strike –slip or transverse fault
A – reverse fault - hanging wall has moved upward
B - Strike-slip fault // Source: indiana.edu
Source: indiana.edu B A
Strike –slip or transverse fault
Hanging wall has moved
upward
Reverse fault

40. Focus
– 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly
Epicenter 2 1

41. People walk along a damaged road in the province of Bohol on Tuesday, October 15, 2013.
Do you think this was a major earthquake? Why or why not?

42. Yes, it was a major quake.
It crumbled a number of buildings
Such as this church
7.1 magnitude earthquake hit the Philippines

43. Earthquakes 3. Surface 1. P-wave 2. S-wave Seismogram
____________ seismic wave display record 4.
Seismograph
5. __________ machine